Hybrid automatic repeat request acknowledge resource allocation for enhanced physical downlink control channel

ABSTRACT

A method and apparatus of wireless communication between a base station and at least one user equipment. The method includes: transmitting an enhanced physical downlink control channel from the base station to the at least one user equipment using a demodulation reference signal antenna port; transmitting message from the base station to the at least one user equipment which is scheduled by the enhanced physical downlink control channel; receiving the message at the at least one user equipment; determining at the at least one user equipment whether the message was correctly received; and transmitting an ACK/NAK signal on an ACK/NAK resource determined from the enhanced physical downlink control channel from the at least one user equipment to the base station indicating whether the message was correctly received by the at least one user.

This application is a Continuation of application Ser. No. 13/526,270filed Jun. 18, 2012, which claims priority under 35 U.S.C. 119(e)(1) toU.S. Provisional Application No. 61/498,063 filed Jun. 17, 2011, whichis incorporated herein by reference in its entirety.

The present embodiments relate to wireless communication systems and,more particularly, to the transmission of Hybrid Automatic RepeatRequest acknowledgments in response to multi-input multi-output (MIMO)transmissions of data and dedicated reference signals withcodebook-based feedback on the the Physical Downlink shared channel(PDCCH).

With Orthogonal Frequency Division Multiplexing (OFDM), multiple symbolsare transmitted on multiple carriers that are spaced apart to provideorthogonality. An OFDM modulator typically takes data symbols into aserial-to-parallel converter, and the output of the serial-to-parallelconverter is considered as frequency domain data symbols. The frequencydomain tones at either edge of the band may be set to zero and arecalled guard tones. These guard tones allow the OFDM signal to fit intoan appropriate spectral mask. Some of the frequency domain tones are setto values which will be known at the receiver. Among these areCell-specific Reference signals (CRS), Channel State InformationReference Signals (CSI-RS) and Dedicated or Demodulating ReferenceSignals (DMRS). These reference signals are useful for channelestimation at the receiver for data demodulation and also to supportlink adaptation at the transmitter. In a multi-input multi-output (MIMO)communication systems with multiple transmit/receive antennas, the datatransmission is performed via precoding. Here, precoding refers to alinear (matrix) transformation of a L-stream data into P-stream where Ldenotes the number of layers (also termed the transmission rank) and Pdenotes the number of transmit antennas. With the use of dedicateduser-specific DMRS, a transmitter (base station, also termed eNodeB oreNB) can perform any precoding operation which is transparent to a userequipment (UE) which acts as a receiver. At the same time, it isbeneficial for the base station to obtain a recommendation on the choiceof precoding matrix from the user equipment. This is particularly thecase for frequency-division duplexing (FDD) where the uplink anddownlink channels occupy different parts of the frequency bands, i.e.the uplink and downlink are not reciprocal. Hence, a codebook-basedfeedback from the UE to the eNodeB is preferred. To enable acodebook-based feedback, a precoding codebook needs to be designed. UEmeasures the downlink MIMO channel and feeds back the channel by usingthe feedback codebook. Specifically, UE reports a precoding matrixindicator (PMI) corresponding to a recommended precoding matrix from thefeedback codebook, as well as channel quality indicators (CQI) whichreflects the receive signal quality when the recommended PMI is used forMIMO precoding.

The Rel. 8 Long-Term Evolution (LTE) specification includes a codebookfor 2-antenna transmissions and a codebook for 4-antenna transmissions.While those codebooks are designed efficiently, they do not supporttransmissions with 8 antennas. Moreover, it is possible to furtherimprove the performance of 4-antenna transmissions under differentscenarios such as dual-polarized antenna arrays. To address theseissues, an 8-Tx codebook was adopted in LTE Rel.10 for the purpose ofchannel feedback for an 8-antenna system.

While the preceding approaches provide steady improvements in wirelesscommunications, the present inventors recognize that still furtherimprovements in downlink (DL) spectral efficiency are possible.Accordingly, the preferred embodiments described below are directedtoward these problems as well as improving upon the prior art.

SUMMARY OF THE INVENTION

A method and apparatus of wireless communication between a base stationand at least one user equipment. The method includes: transmitting anenhanced physical downlink control channel from the base station to theat least one user equipment using a demodulation reference signalantenna port; transmitting message from the base station to the at leastone user equipment which is scheduled by the enhanced physical downlinkcontrol channel; receiving the message at the at least one userequipment; determining at the at least one user equipment whether themessage was correctly received; and transmitting an ACK/NAK signal on anACK/NAK resource determined from the enhanced physical downlink controlchannel from the at least one user equipment to the base stationindicating whether the message was correctly received by the at leastone user.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of this invention are illustrated in thedrawings, in which:

FIG. 1 illustrates an exemplary prior art wireless communication systemto which this application is applicable;

FIG. 2 shows the Evolved Universal Terrestrial Radio Access (E-UTRA)Time Division Duplex (TDD) frame structure of the prior art;

FIG. 3 is a block diagram of a transmitter of the present invention;

FIG. 4 is a block diagram of a receiver of the present invention;

FIG. 5 is a flow diagram of the operation of this invention; and

FIG. 6 is a block diagram illustrating internal details of a basestation and a mobile user equipment in the network system of FIG. 1suitable for implementing this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an exemplary wireless telecommunications network 100. Theillustrative telecommunications network includes base stations 101, 102and 103, though in operation, a telecommunications network necessarilyincludes many more base stations. Each of base stations 101, 102 and 103(eNB) are operable over corresponding coverage areas 104, 105 and 106.Each base station's coverage area is further divided into cells. In theillustrated network, each base station's coverage area is divided intothree cells. Handset or other user equipment (UE) 109 is shown in Cell A108. Cell A 108 is within coverage area 104 of base station 101. Basestation 101 transmits to and receives transmissions from UE 109. As UE109 moves out of Cell A 108 and into Cell B 107, UE 109 may be handedover to base station 102. Because UE 109 is synchronized with basestation 101, UE 109 can employ non-synchronized random access toinitiate handover to base station 102.

Non-synchronized UE 109 also employs non-synchronous random access torequest allocation of up-link 111 time or frequency or code resources.If UE 109 has data ready for transmission, which may be traffic data,measurements report, tracking area update, UE 109 can transmit a randomaccess signal on up-link 111. The random access signal notifies basestation 101 that UE 109 requires up-link resources to transmit the UEsdata. Base station 101 responds by transmitting to UE 109 via down-link110, a message containing the parameters of the resources allocated forUE 109 up-link transmission along with a possible timing errorcorrection. After receiving the resource allocation and a possibletiming advance message transmitted on down-link 110 by base station 101,UE 109 optionally adjusts its transmit timing and transmits the data onup-link 111 employing the allotted resources during the prescribed timeinterval.

Base station 101 configures UE 109 for periodic uplink soundingreference signal (SRS) transmission. Base station 101 estimates uplinkchannel quality information (CSI) from the SRS transmission.

FIG. 2 shows the Evolved Universal Terrestrial Radio Access (E-UTRA)time division duplex (TDD) Frame Structure. Different subframes areallocated for downlink (DL) or uplink (UL) transmissions. Table 1 showsapplicable DL/UL subframe allocations.

TABLE 1 Config- Switch-point Sub-frame number uration periodicity 0 1 23 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D DD D D 5 10 ms D S U D D D D D D D 6 10 ms D S U U U D S U U D

FIG. 3 is a block diagram of a wireless transmitter 200 of the presentinvention for transmitting a preamble 202 to a remote receiver. Thepreamble is preferably a CAZAC sequence for generating the random accesspreamble signal. CAZAC sequences are complex valued sequences withfollowing two properties: 1) Constant Amplitude (CA), and 2) Zero CyclicAutocorrelation (ZAC). Examples of CAZAC sequences include but are notlimited to: Chu Sequences; Frank-Zadoff Sequences; Zadoff-Chu (ZC)Sequences; and Generalized Chirp-Like (GCL) Sequences.

Zadoff-Chu (ZC) sequences are defined by:

${a_{M}(k)} = {e^{\lbrack{j\; 2{{\pi{({M/N})}}{\lbrack{{k\frac{({k + 1})}{2}} + {qk}}\rbrack}}}\rbrack}\mspace{31mu}{for}\mspace{14mu} N\mspace{14mu}{odd}}$${a_{M}(k)} = {e^{\lbrack{j\; 2{{\pi{({M/N})}}{\lbrack{\frac{k^{2}}{2} + {qk}}\rbrack}}}\rbrack}\mspace{31mu}{for}\mspace{14mu} N\mspace{14mu}{even}}$where: N is the length of the sequence; M is the index of the root ZCsequence with M and N being relatively prime; q is any fixed integer;and k is the index of the sequence element ranging from 0 to N−1. Theseare representative examples of CAZAC sequences. An alternativeconvention for ZC definition replaces j in the above formula by −j.Either convention can be adopted. In the above formula, making N a primenumber maximizes the set of non-orthogonal root ZC sequences havingoptimal cross-correlation. When N is prime, there are (N−1) possiblechoices for M. Each such choice results in a distinct root ZC CAZACsequence. In this application the terms Zadoff-Chu, ZC and ZC CAZAC willbe used interchangeably. The term CAZAC denotes any CAZAC sequence, ZCor otherwise.

In a preferred embodiment of the invention, random access preamblesignal 202 is constructed from a CAZAC sequence, such as a ZC sequence.Additional modifications to the selected CAZAC sequence can be performedusing any of the following operations: multiplication by a complexconstant, Discrete Fourier Transform (DFT), inverse Discrete FourierTransform (IDFT), Fast Fourier Transform (FFT), inverse Fast FourierTransform (IFFT), cyclic shifting, zero padding, sequence blockrepetition, sequence truncation, sequence cyclic extension and others.In the preferred embodiment of the invention, UE 200 selects randomaccess preamble signal 202, by selecting a CAZAC sequence and optionallymodified as noted above. DFT circuit 204 receives the modified CAZACsequence to produce a frequency domain signal. Sub-carrier mappingcircuit 206 receives the frequency domain signal. Sub-carrier mappingcircuit maps the preamble to user selected tones. IDFT circuit 208 thenconverts the user selected tones to a time domain signal which issupplied to parallel-to-serial converter 210. The resulting preamble isoptionally repeated to achieve the desired duration. Cyclic prefix (CP)circuit 214 adds a cyclic prefix to the preamble before transmission toa remote receiver.

FIG. 4 is a block diagram of an embodiment of a random access channelreceiver 300 of the present invention. CP removal circuit 302 removesthe cyclic prefix from the received random access signal.Serial-to-parallel converter 304 converts the resulting preamble into aparallel signal. DFT circuit 306 produces sub-carrier mapped tones fromthe parallel preamble components. Sub-carrier de-mapping circuit 308demaps the mapped tones. These demapped tones are equivalent to theoutput signal from DFT circuit 204 of transmitter 200 (FIG. 2).Parallel-to-serial circuit 310 converts the parallel demapped tones intoa serial data stream. Product circuit 312 receives this serial datastream and a reference root sequence from DFT circuit 320. Productcircuit 312 computes a tone by tone complex multiplication of demappedtones with the reference tones. Zero padding circuit 314 adds a numberof zeros necessary to produce a correct sequence length. IDFT circuit316 converts the multiplied frequency tones into time domain signals.These time domain signals include concatenated power delay profiles ofall cyclic shift replicas of the preamble root sequence. Energy detectorcircuit 318 detects the energy in the time domain signals. Thisidentifies the received preamble sequences by detecting the time of peakcorrelation between received random access preamble signals and thereference ZC root sequence.

For DL data transmission from a transmitter to a receiver, acorresponding HARQ-ACK report is transmitted in the uplink from thereceiver to the transmitter. An ACK response indicates a successfuldecoding at the receiver while a NAK indicates a failed decoding. In thecase of a NAK response, a retransmission may be scheduled.

In prior wireless communication systems, ACK/NAK is reported on thephysical uplink control channel (PUCCH) where the PUCCH ACK/NAK resourceis semi-statically configured or can be dynamically allocated. A userequipment can be configured to transmit the ACK/NAK on either PUCCHFormat 1a/1b or PUCCH Format 3. For dynamic allocation the PUCCHresource for FDD is determined as:n _(PUCCH) =n _(CCE) +N _(PUCCH) ⁽¹⁾  (1)where: n_(CCE) is the index of the lowest control channel elements (CCE)in the corresponding physical downlink control channel (PDCCH); andN_(PUCCH) ⁽¹⁾ is a cell-specific offset which delineates the semi-staticPUCCH format 1a/1b region from the dynamic PUCCH format 1a/1b region andis semi-statically configured by higher layer signaling. The PDCCHcarries a downlink grant and conveys the downlink scheduling informationto the UE. The UE performs PDCCH blind decoding to find the downlinkgrant before proceeding to decode the downlink data. The PDCCH may betransmitted with an aggregation level of 1, 2, 4 or 8 control channelelements (CCE). A CCE is the basic unit for control channel resourceallocation. In legacy wireless communications systems such as LTE Rel. 8to 10, the control region is cell-specific designated and allocated inthe first 3 of 4 OFDM symbols in a subframe. CCEs in the common controlregion are indexed as 0 to N_CCE−1. This is commonly known by all UEs.

The PDCCH in legacy LTE Rel. 8 to 10 is designed with Cell-specificReference Symbols (CRS) based transmission. A PDCCH is scrambled withthe Cell-Radio Network Temporary Identifier (C-RNTI) of the user beingscheduled. This is precoded with 1/2/4 transmit (Tx) antenna diversity,cross-interleaved with other PDCCHs and then transmitted in the entiresystem bandwidth in the control region of a subframe. The control regioncontains the first N OFDM symbols in the first slot of a subframe. Theseare N=1, 2, 3 for bandwidths greater than 10 physical resource blocks(PRB) or N=2, 3, 4 otherwise. The value of N is known as the ControlFormat Indicator (CFI) and is signaled on the Physical Control FormatIndicator CHannel (PCFICH). Through CRS-based transmit diversity andcross-interleaving within the system bandwidth, Rel. 10 PDCCH exploitsthe spatial and frequency diversity to maximize the robustness of thecontrol signal and to ensure reliable reception and coverage in a cell.

Enhanced PDCCH is proposed for LTE Rel. 11. Enhanced PDCCH is hereafterreferred to as ePDCCH. The ePDCCH inherits all the Downlink ControlIndicator (DCI) formats of legacy LTE systems including DCI formats 0,1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, and 4. The ePDCCH relies on DMRS basedtransmit diversity rather than CRS based transmit diversity. For each UEa semi-statically configured downlink resource is reserved for ePDCCH.The UE performs blind decoding of the semi-statically configuredresources for the ePDCCH. The ePDCCH is transmitted on a single DMRSantenna port such as antenna port 7 or 8 with a scrambling sequenceidentity (SCID) equal to 0 and DMRS based rank-1 precoding.

Multiuser, Multiple Input, Multiple Output (MU-MIMO) for ePDCCH is alsobeing proposed for LTE Rel. 11 to transmit multiple ePDCCH to differentUEs using the same time/frequency resources. This is an effective meansto increase the ePDCCH capacity by exploiting spatial multiplexing ofthe DL control channel. Exemplary embodiments of MU-MIMO for ePDCCH canbe found in U.S. patent application Ser. No. 13/458,410, entitled“PHYSICAL DOWNLINK CONTROL CHANNEL AND PHYSICAL HYBRID AUTOMATIC REPEATREQUEST INDICATOR CHANNEL ENHANCEMENTS” filed Apr. 27, 2012. The firstePDCCH is transmitted on antenna port 7 with SCID=0. The second ePDCCHis transmitted on antenna port 7, with SCID=1. The third ePDCCH istransmitted on antenna port 8, with SCID=0 or 1.

There is a possible collision of LTE Rel. 11 HARQ-ACK transmissions asfollows. When two ePDCCHs of two UEs are spatial multiplexed withMU-MIMO, it is possible that the ACK/NAK responses of these two Rel. 11UEs are mapped to the same HARQ-ACK resource according to equation (1)if N_(PUCCH) ⁽¹⁾ and n_(CCE) satisfy the same criteria of equation (1).In this case, a new mechanism for determining the HARQ-ACK resource isneeded to avoid HARQ-ACK collision and to ensure reliable HARQ-ACKreception and system performance.

There is also a possible collision of LTE Rel. 10 and Rel. 11 HARQ-ACKas follows. The legacy (LTE Rel. 10) PUCCH resource allocation was basedon the PDCCH region. The ePDCCH is located in the PDSCH region. In orderto reduce the PUCCH overhead it may be necessary to allow some overlapbetween PUCCH region indicated by legacy PDCCH and the PUCCH regionindicated by the ePDCCH. Thus a new PUCCH resource allocation isrequired that can also avoid collisions between ACK/NAK resourcescorresponding to PDSCH transmissions scheduled by either PDCCH orePDCCH.

The ePDCCH can be aggregated in terms of CCEs or in terms of physicalresource blocks (PRBs). Hereafter, the term CCE refers interchangeablyto either the control channel element for the PDCCH or the ePDCCH. Thisinvention is expressed in terms of the CCE index n_(CCE). This inventionis equally applicable when ePDCCH is aggregated in terms of PRB, wheren_(CCE) is replaced by the lowest PRB index n_(PRB). When there is noconfusion, this application uses n_(CCE), n_(PRB) and n_(index)interchangeably.

HARQ-ACK Resource for ePDCCH

In LTE Rel. 11, a cell-specific common control region is needed in manycases such as for support of legacy LTE Rel. 8 to Rel. 10 UEs and forRadio Resource Control (RRC) configuration or reconfiguration of Rel. 11UEs. In this case the common control region and its CCE indexing remainthe same as in Rel. 8 to 10. Then for a Rel. 11 UE configured withePDCCH there are two cases.

For cross-interleaved/CRS-based ePDCCH, the ePDCCH is aggregated interms of CCE. In Extended indexing the CCE in the ePDCCH region isindexed from N_(CCE) to N_(CCE)+M_(CCE)−1, where M_(CCE) is the numberof CCEs in the ePDCCH region. In Separate indexing the CCE in the ePDCCHregion are indexed from 0 to M_(CCE)−1.

For non-cross-interleaved/DMRS-based ePDCCH, the ePDCCH is aggregated interms of PRB. In Extended indexing the PRB in the ePDCCH region isindexed from N_(CCE) a to N_(CCE)+M_(PRB)−1, where M_(PRB) is the numberof PRB in the ePDCCH region. In Separate indexing the PRB in the ePDCCHregion are indexed from 0 to M_(PRB)−1.

In both cases the ePDCCH region is UE specific and each UE has noknowledge of the existence or the size of the ePDCCH configuration ofthe other UE. Thus, different CCEs in different ePDCCH regions of thetwo UEs may end up with the same CCE index. This leads to collision ofACK/NAK resources.

For example suppose UE1 is configured with an ePDCCH region of 6resource blocks (RBs) in PRB [0-5] and ePDCCH1 is transmitted with 1-PRBaggregation level on PRB 1. Suppose also UE2 is configured with anePDCCH region of 6 RB in PRB [6-11] and ePDCCH2 is transmitted with1-PRB aggregation level, on PRB7. In this case ePDCCH1 and ePDCCH2 bothhave n_(index)=1 and therefore their ACK/NAK resources collide.

In a first embodiment of this invention for ePDCCH withno-cross-interleaving/DMRS-based transmission, the ePDCCH is indexed bythe position of its lowest PRB in the entire system bandwidth. Thus eachPRB in the system bandwidth is indexed as 0−N_(DL)−1, where N_(DL) isthe downlink system bandwidth expressed in PRBs. For example suppose UE1is configured with ePDCCH region of 6 RBs in PRB [0-5] and ePDCCH1 istransmitted with 1-PRB aggregation level on PRB 1. Suppose also that UE2is configured with ePDCCH region of 6 RB, in PRB [6-11] and ePDCCH2 istransmitted with 1-PRB aggregation level on PRB7. In accordance withthis embodiment ePDCCH1 is indexed as n_(index)=1 and ePDCCH2 is indexedas n_(index)=7.

The inventors expect that early deployments of LTE Rel. 11 systems wouldsupport only a limited number of Rel. 11 UEs. Thus backward compatibleserving cells should contain the legacy control regions to support Rel.8/9/10 UEs. If only a few Rel. 11 UEs are configured to receive DCI onthe ePDCCH, the PUCCH DCI format 1a/1b/3 resource for such UEs can besemi-statically configured.

The overhead for the semi-static allocation is not expected to be largeif only a few Rel. 11 UEs are scheduled in a subframe. One possibilityto reduce the overhead of semi-static configuration of PUCCH DCI format1a/1b resources is to configure the UE with a set of four PUCCHresources and dynamically indicate the assigned PUCCH resource using aHARQ-ACK resource indicator (ARI). This is similar to the resourceallocation procedure for PUCCH DCI format 3 in Rel. 10. A side benefitof this approach is that the ARI can be used to avoid collisions in thecase of partial overlap between the PUCCH regions indicated by Rel. 8 to10 PDCCH and the Rel. 11 and beyond ePDCCH.

To minimize the change from legacy resource allocation the same formulain equation (1) can be modified for Rel. 11 HARQ-ACK resourceallocation. If a DMRS-based PRB-specific ePDCCH is configured, thelowest-indexed PRB for the ePDCCH can be used in place of the CCE index.If CRS-based ePDCCH is possible in Rel. 11, an extended CCE indexingscheme beyond Rel. 10 can be used for the resource allocation. Anenhanced dynamic PUCCH DCI format 1a/1b region can be defined by a newoffset parameter denoted N_(PUCCH,e) ⁽¹⁾. In this embodiment the dynamicPUCCH region is sub-divided into a legacy region and an enhanced region.When a Rel. 11 UE is configured by higher layers to receive its DCI onthe ePDCCH and also to use DCI format 1a/1b for HARQ-ACK transmission itdetermines its HARQ-ACK resource as:n _(PUCCH) ⁽¹⁾ =n _(index) +N _(PUCCH) ⁽¹⁾ +g(N _(PUCCH,e) ⁽¹⁾)  (2)where: n_(index) can be the lowest indexed PRB or lowest indexed CCE;and g(N_(PUCCH,e) ⁽¹⁾) is a function of the extended offset parameter,which can be defined based on the ePDCCH type.

If a CRS-based ePDCCH is defined, the same concept of CCEs is usedwherein 0, . . . , N_(CCE,k)−1 is the set of Rel. 10 CCEs in subframe kand N_(CCE,k), . . . , M_(CCE,k)−1 defines the set of Rel. 11 CCEscorresponding to the ePDCCH and g(N_(PUCCH,e) ⁽¹⁾)=0. Thus the HARQ-ACKresource allocation for the ePDCCH is a straightforward extension of theRel. 8/9/10 technique. The particular implementation of the eNBdimensions the PUCCH region to support HARQ-ACK resources correspondingto the DCI scheduled on both the PDCCH and ePDCCH. This embodimentprecludes spatial multiplexing of DCIs for multiple UEs on the same CCEsbecause this would result in HARQ-ACK resource collision.

An example of the DMRS-ePDCCH is g(N_(PUCCH,e) ⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾where the Rel. 11 PUCCH HARQ-ACK resource allocation is based on thelowest-indexed PRB for the ePDCCH allocation n_(PRB). Similarly the eNBshould dimension the PUCCH region appropriately. Extensions to thisscheme is required when two or more UEs receive their controlinformation on the same physical or logical resources as describedbelow.

Note that g(N_(PUCCH,e) ⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾ can be UE-specific. Forexample UE1 can be configured with g(N_(PUCCH,e) ⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾and UE2 is configured with g(N_(PUCCH,e) ⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾+1. TheACK/NAK responses of UE1 and UE2 will not collide even if ePDCCHs ofthese two UEs are multiplexed and share the same CCE index. In analternative embodiment g(N_(PUCCH,e) ⁽¹⁾) can encompass the totalUE-specific offset and the HARQ-ACK resource is determined as:n _(PUCCH) ⁽¹⁾ =n _(index) +g(N _(PUCCH,e) ⁽¹⁾)  (3)

The HARQ-ACK resource can be further determined as a function of thescrambling sequence on the CRC of the corresponding ePDCCH:n _(PUCCH) ⁽¹⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +N _(PUCCH,e) ⁽¹⁾+g′(CRC_scrambling_sequence_ID)For example, two scrambling sequences can be defined to mask the CRCbits of an ePDCCH. A first ePDCCH with CRC scrambled by scramblingsequence ID 1 transmits HARQ-ACK resource on N_(PUCCH)⁽¹⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾+N_(PUCCH,e) ⁽¹⁾+0, while a second ePDCCH withCRC scrambled by scrambling sequence ID 2 transits HARQ-ACK resource onn_(PUCCH) ⁽¹⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾+N_(PUCCH,e) ⁽¹⁾+1. By dynamicallyselecting the CRC scrambling sequence, the network is able todynamically configure the HARQ-ACK resource of a UE.

The HARQ-ACK resource is further determined as a function of the DMRSantenna port of the corresponding ePDCCH downlink grant:n _(PUCCH) ⁽¹⁾ =n _(CCE) +N _(PUCCH) ⁽¹⁾ +N _(PUCCH,e) ⁽¹⁾+g′(DMRS_port_PDCCH)For example, if g(x)=x−7, then the HARQ-ACK corresponding to ePDCCH onantenna port 7 is transmitted on HARQ-ACK resourcen_(PUCCH)=n_(CCE)+f(N_(PUCCH))+0, while the HARQ-ACK corresponding toePDCCH on antenna port 8 is transmitted on HARQ-ACK resourcen_(PUCCH)=n_(CCE)+f(N_(PUCCH))+1.

The HARQ-ACK resource is further determined as a function of the DMRSscrambling sequence identity (SCID) of the corresponding ePDCCH:n _(PUCCH) =n _(CCE) +f(N _(PUCCH))+g(SCID_PDCCH)For example, if g(x)=x, then the HARQ-ACK corresponding to an ePDCCHwith SCID=0 is transmitted on HARQ-ACK resourcen_(PUCCH)=n_(CCE)+f(N_(PUCCH))+0 and HARQ-ACK corresponding to an ePDCCHwith SCID=1 is transmitted on HARQ-ACK resourcen_(PUCCH)=n_(CCE)+f(N_(PUCCH))+1.

It is further possible to use the combination of prior embodiments or asubset thereof, to determine the PUCCH HARQ-ACK resources. For example,the HARQ-ACK resource is determined as a function of the DMRS antennaport ID and SCID of the corresponding ePDCCH as:n _(PUCCH) =n _(CCE) +f(N _(PUCCH))+g(SCID_PDCCH,DMRS_port_PDCCH)where: an exemplary function of g( ) is given as:

TABLE 2 g (SCID_PDCCH, SCID_PDCCH DMRS_port_PDCCH DMRS_port_PDCCH) 0 7 01 7 1 0 8 2 1 8 3

TABLE 3 g (SCID_PDCCH, SCID_PDCCH DMRS_port_PDCCH DMRS_port_PDCCH) 0 7 00 8 1 1 7 2 1 8 3Yet another possible example is given by:n _(PUCCH) =n _(CCE) +f(N _(PUCCH))+N _(CCE)×g(SCID_PDCCH,DMRS_port_PDCCH)where: N_(CCE) is the total number of available CCEs for ePDCCH on asingle antenna port with a single SCID without MU-MIMO of ePDCCH. Thephysical interpretation of this approach can be explained as follows:MU-MIMO for ePDCCH essentially increases the ePDCCH capacity by creatingmore control resources that are associated with multiple antenna portsand multiple SCID. For the conventional ePDCCH transmitted on port 7with SCID=0, the CCE indexing follow the conventional indexing from 0 toN_(CCE)−1. For additional ePDCCH resources on an additional antenna portand SCID, the CCE indexing is incremented by a fudge factor to reflectthe ePDCCH resource increase. For example according to Table 2: theePDCCH on antenna port 7 with SCID 1 are indexed as N_(CCE), N_(CCE)+1,. . . 2N_(CCE)−1; the ePDCCH on antenna port 8 with SCID 0 are indexedas 2N_(CCE), 2N_(CCE)+1, . . . 3N_(CCE)−1; and the ePDCCH on antennaport 8 with SCID 1 are indexed as 3N_(CCE), 3N_(CCE)+1, . . .4N_(CCE)−1.

FIG. 5 illustrates the message/data flow in accordance with thisinvention. As noted in FIG. 5 operations left of the dashed line arepreformed by a base station and operations right of the dashed line areperformed by a user equipment.

The base station semi-statically transmits a radio frequency signal 512to configure the HARQ-ACK parameters of a user equipment. As noted abovethese are transmitted via higher-layer signaling. The configuredHARQ-ACK parameters includes those described above. In 521 the userequipment receives these parameter indicators and configures itsHARQ-ACK parameters accordingly. As noted above the base station mayconfigure HARQ-ACK parameters on a cell-specific basis. In that eventtransmission 512 is typically coded for only the user equipment beingconfigures. The base station may configure the same HARQ-ACK parametersfor all user equipment within the cell it serves. In that eventtransmission 512 is typically coded for all user equipment within thecell. As hinted in the semi-statically description this transmissiontakes place periodically but less often than every message 531(described below).

At a later and generally unrelated time the base station transmits amessage 531 via radio frequency signal 532. This message can be thevoice of an ordinary voice telephone call or data previously requestedby the user equipment. The user equipment receives this message at 541.

The user equipment determines if the message was correctly received indecision block 542. Each message transmission typically includesredundancy in the form of an error correcting code. The user equipmentuses this error correcting code to determine if the message wascorrectly received. If the message was correctly received (Yes atdecision block 542), then the user equipment selects a acknowledge (ACK)response in block 543. If the message was incorrectly received (No atdecision block 542), then the user equipment selects a non-acknowledge(NAK) response in block 544. The user equipment transmits the selectedACK or NAK response on the configured resource in block 545 via radiofrequency signal 546 to the base station.

The base station receives the ACK/NAK response on the configuredresource in 533. If the ACK/NAK response is an acknowledgement (Yes atdecision block 534), then the base station continues with its operation.Depending upon the current status transmission to the base station maybe complete or the base station may transmit an addition message ormessages to the user equipment. If the ACK/NAK response is anon-acknowledgement (No at decision block 534), then the base stationtakes remedial action at block 536. As known in the art this remedialaction may include retransmission of the message, further communicationbetween the base station and the user equipment to identify the error orthe like.

FIG. 6 is a block diagram illustrating internal details of an eNB 902and a mobile UE 901 in the network system of FIG. 1. Mobile UE 901 mayrepresent any of a variety of devices such as a server, a desktopcomputer, a laptop computer, a cellular phone, a Personal DigitalAssistant (PDA), a smart phone or other electronic devices. In someembodiments, the electronic mobile UE 901 communicates with eNB 902based on a LTE or Evolved Universal Terrestrial Radio Access Network(E-UTRAN) protocol. Alternatively, another communication protocol nowknown or later developed can be used.

Mobile UE 901 comprises a processor 910 coupled to a memory 912 and atransceiver 920. The memory 912 stores (software) applications 914 forexecution by the processor 910. The applications could comprise anyknown or future application useful for individuals or organizations.These applications could be categorized as operating systems (OS),device drivers, databases, multimedia tools, presentation tools,Internet browsers, emailers, Voice-Over-Internet Protocol (VOIP) tools,file browsers, firewalls, instant messaging, finance tools, games, wordprocessors or other categories. Regardless of the exact nature of theapplications, at least some of the applications may direct the mobile UE901 to transmit UL signals to eNB (base-station) 902 periodically orcontinuously via the transceiver 920. In at least some embodiments, themobile UE 901 identifies a Quality of Service (QoS) requirement whenrequesting an uplink resource from eNB 902. In some cases, the QoSrequirement may be implicitly derived by eNB 902 from the type oftraffic supported by the mobile UE 901. As an example, VOIP and gamingapplications often involve low-latency uplink (UL) transmissions whileHigh Throughput (HTP)/Hypertext Transmission Protocol (HTTP) traffic caninvolve high-latency uplink transmissions.

Transceiver 920 includes uplink logic which may be implemented byexecution of instructions that control the operation of the transceiver.Some of these instructions may be stored in memory 912 and executed whenneeded by processor 910. As would be understood by one of skill in theart, the components of the uplink logic may involve the physical (PHY)layer and/or the Media Access Control (MAC) layer of the transceiver920. Transceiver 920 includes one or more receivers 922 and one or moretransmitters 924.

Processor 910 may send or receive data to various input/output devices926. A subscriber identity module (SIM) card stores and retrievesinformation used for making calls via the cellular system. A Bluetoothbaseband unit may be provided for wireless connection to a microphoneand headset for sending and receiving voice data. Processor 910 may sendinformation to a display unit for interaction with a user of mobile UE901 during a call process. The display may also display picturesreceived from the network, from a local camera, or from other sourcessuch as a Universal Serial Bus (USB) connector. Processor 910 may alsosend a video stream to the display that is received from various sourcessuch as the cellular network via RF transceiver 920 or the camera.

During transmission and reception of voice data or other applicationdata, transmitter 924 may be or become non-synchronized with its servingeNB. In this case, it sends a random access signal. As part of thisprocedure, it determines a preferred size for the next datatransmission, referred to as a message, by using a power threshold valueprovided by the serving eNB, as described in more detail above. In thisembodiment, the message preferred size determination is embodied byexecuting instructions stored in memory 912 by processor 910. In otherembodiments, the message size determination may be embodied by aseparate processor/memory unit, by a hardwired state machine, or byother types of control logic, for example. eNB 902 comprises a Processor930 coupled to a memory 932, symbol processing circuitry 938, and atransceiver 940 via backplane bus 936. The memory stores applications934 for execution by processor 930. The applications could comprise anyknown or future application useful for managing wireless communications.At least some of the applications 934 may direct eNB 902 to managetransmissions to or from mobile UE 901.

Transceiver 940 comprises an uplink Resource Manager, which enables eNB902 to selectively allocate uplink Physical Uplink Shared CHannel(PUSCH) resources to mobile UE 901. As would be understood by one ofskill in the art, the components of the uplink resource manager mayinvolve the physical (PHY) layer and/or the Media Access Control (MAC)layer of the transceiver 940. Transceiver 940 includes at least onereceiver 942 for receiving transmissions from various UEs within rangeof eNB 902 and at least one transmitter 944 for transmitting data andcontrol information to the various UEs within range of eNB 902.

The uplink resource manager executes instructions that control theoperation of transceiver 940. Some of these instructions may be locatedin memory 932 and executed when needed on processor 930. The resourcemanager controls the transmission resources allocated to each UE 901served by eNB 902 and broadcasts control information via the PDCCH.

Symbol processing circuitry 938 performs demodulation using knowntechniques. Random access signals are demodulated in symbol processingcircuitry 938.

During transmission and reception of voice data or other applicationdata, receiver 942 may receive a random access signal from a UE 901. Therandom access signal is encoded to request a message size that ispreferred by UE 901. UE 901 determines the preferred message size byusing a message threshold provided by eNB 902. In this embodiment, themessage threshold calculation is embodied by executing instructionsstored in memory 932 by processor 930. In other embodiments, thethreshold calculation may be embodied by a separate processor/memoryunit, by a hardwired state machine, or by other types of control logic,for example. Alternatively, in some networks the message threshold is afixed value that may be stored in memory 932, for example. In responseto receiving the message size request, eNB 902 schedules an appropriateset of resources and notifies UE 901 with a resource grant.

What is claimed is:
 1. A user equipment, comprising: a transceiver; adata processor connected to said transceiver; and a memory connected tosaid digital data processor storing data and at least one applicationprogram controlling operation of said data processor, said at least oneapplication program operable to control said data processor to receive acontrol message on an enhanced physical downlink control channel(EPDCCH); receive a second message indicated by the control message;receive a demodulation reference signal on the same antenna port as theassociated EPDCCH physical resource; transmit an ACK/NAK signal on anACK/NAK resource determined from the EPDCCH indicating whether thesecond message was correctly received by the user equipment; transmitthe ACK/NACK using physical uplink control channel format 1a or 1bwherein the PUCCH resource is determined for at least one EPDCCHphysical resource block set according to:n _(PUCCH) ⁽¹⁾ =n _(index) +N _(PUCCH) ⁽¹⁾ +g(N _(PUCCH,e) ⁽¹⁾) wheren_(index) is the respective lowest indexed physical resource block orlowest indexed control channel element; N_(PUCCH) ⁽¹⁾ is thecell-specific offset; N_(PUCCH,e) ⁽¹⁾ is determined from a resourceoffset field corresponding to the EPDCCH, and g(N_(PUCCH,e) ⁽¹⁾) is afunction of N_(PUCCH,e) ⁽¹⁾.
 2. The user equipment of claim 1, wherein:said at least one application program is further operable to controlsaid data processor to receive a signal to determine the selection ofACK/NAK resources for transmission of the ACK/NAK signal.
 3. The userequipment of claim 1, wherein: said at least one application programenables said data processor to receive a signal employing a physicaluplink control channel downlink control indicator format 1a or 1b or 3resource for semi-static configuration including semi-staticallyconfiguring the user equipment with a set of four physical uplinkcontrol channel resources and indicating a currently assigned physicaluplink control channel resource using a hybrid automatic repeat requestacknowledge resource indicator.
 4. The user equipment of claim 1,wherein: said N_(PUCCH,e) ⁽¹⁾ is determined using a downlink controlinformation (DCI) field.
 5. The user equipment of claim 1, wherein:g(N_(PUCCH,e) ⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾.
 6. The user equipment of claim 1,wherein g(N_(PUCCH,e) ⁽¹⁾) is a function N_(PUCCH,e) ⁽¹⁾ and the controlchannel elements configured in certain subframes.
 7. The user equipmentof claim 1, wherein the data processor is a digital data processor. 8.The user equipment of claim 7, wherein the digital data processor isprogrammable.
 9. A method of operating a user equipment, comprising:receiving a control message on an enhanced physical downlink controlchannel (EPDCCH); receiving a second message indicated by the controlmessage; receiving a demodulation reference signal associated with theEPDCCH; transmitting an ACK/NAK signal on an ACK/NAK resource determinedfrom the EPDCCH indicating whether the second message was correctlyreceived by the user equipment; transmitting the ACK/NACK using physicaluplink control channel format 1a or 1b wherein the PUCCH resource isdetermined for at least one EPDCCH physical resource block set accordingto:n _(PUCCH) ⁽¹⁾ =n _(index) +N _(PUCCH) ⁽¹⁾ +g(N _(PUCCH,e) ⁽¹⁾) wheren_(index) is the respective lowest indexed physical resource block orlowest indexed control channel element; N_(PUCCH) ⁽¹⁾ is thecell-specific offset; N_(PUCCH,e) ⁽¹⁾ is determined from a resourceoffset field corresponding to the EPDCCH, and g(N_(PUCCH,e) ⁽¹⁾) is afunction of N_(PUCCH,e) ⁽¹⁾.
 10. The method of claim 9, furthercomprising: receiving a signal for determining the selection of ACK/NAKresources for transmission of the ACK/NAK signal.
 11. The method ofclaim 9, further comprising: receiving a signal employing a physicaluplink control channel downlink control indicator format 1a or 1b or 3resource for semi-static configuration including semi-staticallyconfiguring the user equipment with a set of four physical uplinkcontrol channel resources and indicating a currently assigned physicaluplink control channel resource using a hybrid automatic repeat requestacknowledge resource indicator.
 12. The method of claim 9, wherein: saidN_(PUCCH,e) ⁽¹⁾ is determined using a downlink control information (DCI)field.
 13. The method of claim 9, wherein: g(N_(PUCCH,e)⁽¹⁾)=N_(PUCCH,e) ⁽¹⁾.
 14. The method of claim 9, wherein g(N_(PUCCH,e)⁽¹⁾) is a function N_(PUCCH,e) ⁽¹⁾ and the control channel elementsconfigured in certain subframes.
 15. A user equipment, comprising:circuitry for receiving a control message on an enhanced physicaldownlink control channel (EPDCCH); circuitry for receiving a secondmessage indicated by the control message; circuitry for receiving ademodulation reference signal on a same antenna port as the associatedEPDCCH physical resource; circuitry for transmitting an ACK/NAK signalon an ACK/NAK resource determined from the EPDCCH indicating whether thesecond message was correctly received by the user equipment; andcircuitry for transmitting the ACK/NACK using physical uplink controlchannel format 1a or 1b wherein the PUCCH resource is determined for atleast one EPDCCH physical resource block set according to:n _(PUCCH) ⁽¹⁾ =n _(index) +N _(PUCCH) ⁽¹⁾ +g(N _(PUCCH,e) ⁽¹⁾) wheren_(index) is the respective lowest indexed physical resource block orlowest indexed control channel element; N_(PUCCH) ⁽¹⁾ is thecell-specific offset; N_(PUCCH,e) ⁽¹⁾ is determined from a resourceoffset field corresponding to the EPDCCH, and g(N_(PUCCH,e) ⁽¹⁾) is afunction of N_(PUCCH,e) ⁽¹⁾.
 16. The user equipment of claim 15, furthercomprising: circuitry for receiving a signal for determining theselection of ACK/NAK resources for transmission of the ACK/NAK signal.17. The user equipment of claim 15, further comprising: circuitry forreceiving a signal employing a physical uplink control channel downlinkcontrol indicator format 1a or 1b or 3 resource for semi-staticconfiguration including semi-statically configuring the user equipmentwith a set of four physical uplink control channel resources andindicating a currently assigned physical uplink control channel resourceusing a hybrid automatic repeat request acknowledge resource indicator.18. The user equipment of claim 15, wherein: said N_(PUCCH,e) ⁽¹⁾ isdetermined using a downlink control information (DCI) field.
 19. Theuser equipment of claim 15, wherein: g(N_(PUCCH,e) ⁽¹⁾=N_(PUCCH,e) ⁽¹⁾.20. The user equipment of claim 15, wherein g(N_(PUCCH,e) ⁽¹⁾) is afunction N_(PUCCH,e) ⁽¹⁾ and the control channel elements configured incertain subframes.